Prepare 1 recipe of my original Homemade Lemon Curd. You'll need some for the filling and some for the topping.
Allow the lemon curd to cool completely in the refrigerator. This can be made ahead of time and stored in the fridge.
Making the Filling:
Place the mascarpone cheese into a large mixing bowl. I don’t recommend warming the cheese; use it straight from the fridge. Add the confectioner’s sugar, vanilla extract, and lemon zest.
Beat the cheese for 3 to 4 minutes on medium speed until it’s thick and creamy. Gradually begin adding the chilled heavy cream, about ½ cup at a time, whisking after each addition.
Once all the heavy cream is added, continue to whisk the filling for a few minutes, until it’s thick and fluffy.
Add 1 cup of chilled lemon curd to the filling and mix until it’s completely incorporated into the filling.
Assembling the Tiramisu:
You can assemble the dessert by layering the cookies and filling into a casserole pan, a large trifle bowl, or individual dessert cups.
In a shallow bowl or tray, combine the lemon juice, limoncello, and water. Dip each lady finger cookie briefly into the mixture, soaking it just until the cookie is soft on the outside but NOT completely soggy and soaked through.
Layer the cookies into the casserole tray in a single layer. Add half the prepared tiramisu filling over the cookies and use a spatula to spread it evenly to the edges.
Add a second layer of cookies, followed by the remaining filling. Pour the remaining lemon curd (approximately 1 ¼ cups) over the top and smooth it with a spatula.
Chilling, Garnishing, & Serving:
Refrigerate the lemon tiramisu for at least 6 hours, or overnight.
Once the lemon tiramisu has chilled and set, whip up a simple whipped cream to garnish the top. Simply whisk together chilled heavy cream, confectioner’s sugar, and vanilla for a few minutes to stiff peaks.
Pipe the whipped cream on top of the tiramisu, then garnish with lemon slices. Cut the dessert into squares, lift with a spatula, then enjoy!